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| <!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" | |
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| <concept id="cwlistbn" xml:lang="en-us"> | |
| <title>Listeners</title> | |
| <prolog><metadata> | |
| <keywords><indexterm>listeners<indexterm>overview</indexterm></indexterm> | |
| </keywords> | |
| </metadata></prolog> | |
| <conbody> | |
| <p>Listeners are new feature in the <cite>Sun | |
| Microsystems <tm tmclass="special" tmowner="Sun Microsystems, Inc." tmtype="tm" | |
| trademark="Java">Java</tm> Servlet 2.3 Specification</cite>. A listener can be used to monitor and | |
| react to events in a servlet's life-cycle by defining methods that get | |
| invoked when life-cycle events occur. Support for application level | |
| events is defined in the Java Servlet Specification 2.3.</p> | |
| <p>Application event listeners are classes that | |
| implement one or more of the servlet event listener interfaces. Servlet | |
| event listeners support notification for state changes in the | |
| <b>ServletContext</b> and <b>HttpSession</b> objects, specifically: | |
| <ul> | |
| <li><b>Servlet context listeners</b> are used to manage resources or state held at a VM | |
| level for the application.</li> | |
| <li><b>HTTP session listeners</b> are used to manage state or resources associated with a | |
| series of requests made in a Web application from the same client or | |
| user.</li> | |
| </ul></p> | |
| <p>For more information about listeners, refer to the <cite>Sun Microsystems <tm | |
| tmclass="special" tmowner="Sun Microsystems, Inc." tmtype="tm" trademark="Java">Java</tm> Servlet | |
| 2.3 Specification</cite> at <codeph>java.sun.com/products/servlet/download.html</codeph>.</p> | |
| </conbody> | |
| </concept> |